Intraperitoneal Exposure Research Articles

Uptake, tissue distribution and excretion of domoic acid after oral exposure in coho salmon ( Oncorhynchus kisutch)

Domoic acid (DA) is a potent neurotoxin naturally produced by some pennate diatom species of the genus Pseudo-nitzschia. It is well known that during harmful algal blooms fish can accumulate DA in the gastrointestinal (GI) tract and act as vectors of the toxin to higher trophic level piscivores, often with severe neurotoxic consequences to the predators. Although neurotoxicity and mass mortality have been observed in vertebrates (i.e. marine mammals and sea birds) feeding on contaminated fish, to date there has been no evidence of neurobehavioral toxicity in the fish vectors themselves. It has been hypothesized that fish may not absorb DA from the digestive tract, thus making them insensitive to dietary consumption of DA. To test this hypothesis, we performed oral gavage exposures followed by a time series of tissue dissections to characterize uptake, depuration, and tissue distribution of DA in fish. Intracoelomic (IC) injection exposures (which bypass the GI tract) were also performed to determine if coho neurons are neurologically susceptible to DA. Excitotoxic symptoms were observed in fish via IC injection at similar toxin levels that have been reported to induce excitotoxic symptoms in intraperitoneal (IP) exposures with mammalian models such as mice, suggesting that fish neurons have a similar sensitivity to DA as other vertebrates. Surprisingly, after oral gavage with ecologically relevant doses of DA, the toxin was detected in plasma collected from the dorsal aorta via a permanent intraarterial catheter within 15 min, yet excitotoxic symptoms were not observed. Additionally, DA was detected in liver, heart, spleen, kidney, muscle, brain and bile. These data indicate that although DA is absorbed from the gut, fish do not exhibit neuroexcitatory effects at maximum ecologically relevant oral doses of DA. Tissue distribution and DA uptake and depuration patterns suggest that a majority of the absorbed toxin is excreted via the kidneys and bile, thereby preventing toxic levels of DA from reaching sensitive nervous tissue. Additionally, greater than 20% of total IC administered DA doses were sequestered in bile within 1 h of injection in five symptomatic fish, providing evidence for biliary sequestration of the toxin from blood. Here, we comprehensively describe the uptake, depuration, and tissue distribution patterns of DA and propose that renal and biliary processes may serve as primary routes of toxin clearance in fish.

Histopathological evidence of antagonistic effects of tributyltin on benzo[a]pyrene toxicity in the Arctic charr (Salvelinus alpinus)

We previously reported that long-term (54 days), repeated intraperitoneal exposure to low doses of tributyltin (TBT; 0.3 mg/kg) inhibited the metabolic activation of co-administered benzo[a]pyrene (BaP; 3 mg/kg) in the Arctic charr (Salvelinus alpinus); BaP, in turn, stimulated the metabolism and/or excretion of TBT. Here, we report the results of histopathological examinations of liver, kidney and pseudobranch tissue samples originating from these same fish. The results revealed higher lesion incidences at all sampling time points (Days 8, 32 and 56) among BaP-exposed fish compared with fish exposed to either TBT alone or combined with BaP. The severity of lesions like necrosis was also higher in BaP-exposed fish. Moreover, hepatic basophilic foci were observed exclusively in fish exposed to BaP alone. Together, these results provide new evidences that TBT can antagonize BaP toxicity in fish exposed to both pollutants under controlled laboratory conditions. In contrast, BaP does not appear to provide protection against TBT toxicity.

Oral toxicity of the cyanobacterial toxin cylindrospermopsin in mice: Long‐term exposure to low doses

The hepatotoxin cylindrospermopsin, a sulfated-guanidinium alkaloid with substituted dioxypyrimidine (uracil) moiety, was isolated from several cyanobacteria species. The acute toxicity of cylindrospermopsin was well established based on intraperitoneal and oral exposure; however, only a few long-term subacute exposure studies were performed to permit a reliable guideline value for cylindrospermopsin in drinking water. In the study reported herein, female and male mice were exposed to cylindrospermopsin in their drinking water. Cylindrospermopsin-containing, Aphanizomenon ovalisporum (cyanobacterium)-free medium was provided as the only source of drinking water, whereas a control group was given a fresh medium for cyanobacteria as drinking water. Over a period of 42 weeks, experiment groups were exposed to cylindrospermopsin concentration, gradually increased from 100 to 550 microg L(-1) (daily exposure ranged between 10 and 55 microg kg(-1) day(-1)). Body and organ weights were recorded, and serum and hematology analyses were performed 20 and 42 weeks after the beginning of the experiment. The most pronounced effect of cylindrospermopsin was elevated hematocrit levels in both male and female mice after 16 weeks of exposure to cylindrospermopsin. The observed changes in the hematocrit level were accompanied by deformation of red blood cells, which were changed into acanthocyte. Based on these results, a daily cylindrospermopsin dose of 20 microg kg(-1) day(-1) (equivalent to 200 microg L(-1)) is proposed as the lowest-observed-adverse-effect level for both male and female mice.

Cadmium distribution and metallothionein expression in lizard tissues following acute and chronic cadmium intoxication

The present report is an attempt to investigate the influence of intraperitoneal and dietary cadmium exposure on the distribution of cadmium accumulation and induction of metallothionein gene expression in different tissues of the lizard Podarcis sicula. Cadmium accumulation in liver, kidney, ovary, brain and intestine was measured by atomic absorption spectrometry. Metallothionein gene induction was determined by dot blot analyses on the total RNA extracted from the same organs. Our data indicate that cadmium exposure results in significant cadmium uptake, but the patterns of this uptake varies with organ and exposure route. After a single intraperitoneal treatment, concentrations of cadmium and metallothionein transcript are positively correlated in kidney, liver and ovary. Following a dietary cadmium treatment, a positive correlation between the increase of metallothionein mRNA and cadmium accumulation is found in intestine, ovary and kidney, while no correlation is present in liver and brain.

Identification of early molecular pathways affected by paraquat in rat lung

We have used global gene expression profiling, combined with pathway analysis tools, to identify in rats the molecular events associated with paraquat toxicity in the lung. Early (2, 8 and 18 h) gene expression changes induced following intraperitoneal (i.p.) exposure to paraquat were measured in the caudal lobe of lungs using Affymetrix rat genome GeneChips (31,042 probe sets). A single high dose of paraquat dichloride (20 mg/kg) was used that has been shown previously to cause in rats extensive lung fibrosis after 10 days. Hierarchical clustering of 543 paraquat-responsive genes (false discovery rate < 0.05) revealed that under these conditions of exposure paraquat induces a staged transcriptional response in the rat lung that precedes the appearance of lung damage. We report here that many of the transcriptional responses to paraquat were rapid (being maximal at 2 h post-dose), and that the predominant molecular functions and biological processes associated with these genes include membrane transport, oxidative stress, lung development, epithelial cell differentiation and transforming growth factor β (TGF-β) signalling. These data provide novel insights into the molecular pathways that lead to toxicity after exposure of the rat lung to paraquat.

Peritoneal Dialysis Fluid–Induced Angiogenesis in Rat Mesentery Is Increased by Lactate in the Presence or Absence of Glucose

Angiogenesis may be an important mechanism behind the functional deterioration of the peritoneum leading to ultrafiltration failure in peritoneal dialysis. The present study was designed to compare the angiogenic properties of lactate-, bicarbonate-, and pyruvate-buffered fluids, evaluated separately with and without glucose. Five different fluids (lactate and bicarbonate with and without 2.5% glucose and pyruvate without glucose) were studied for 5 weeks of twice-daily injections in rats. The respective buffers (40 mmol/l) were adjusted to pH 7.2, and sodium, chloride, calcium, and magnesium were present at standard concentrations. The mesenteric window model, based on observation of the translucent peritoneal sections of the small intestine mesentery, was used for immunohistochemical imaging of microvessels (RECA-1 antigen) and macrophages (ED1 and ED2 antigens). All fluids induced angiogenesis as compared with untreated controls. The lactate-buffered fluids induced larger vascularized zones than did their bicarbonate- and pyruvate-buffered counterparts. Angiogenesis was accompanied by a local recruitment of ED1 macrophages from blood. Addition of glucose to the lactate- and bicarbonate-buffered fluids did not seem to alter their pro-angiogenic properties. In conclusion, intraperitoneal exposure to lactate buffer, compared with bicarbonate, stimulates angiogenesis in the presence or absence of glucose.

Kinetic of Genotoxic Expression in the Pharmacodynamics of Busulfan

Busulfan (BUS) is a highly toxic antineoplastic bifunctional-alkylating agent and has a narrow therapeutic window. Our previous study revealed a narrow dose-range of BUS, which causes a sudden dose-dependent transition from early- to late-expressing micronucleus induction and from a non-cytotoxic to a cytotoxic effect. In the present study, the kinetics of DNA-damaged cell induction by BUS and its dose-effect relationship were established. This was achieved by using the kinetics of DNA-damaged cell induction, determined by the comet assay in murine peripheral blood leukocytes of mice, after the intraperitoneal exposure to 16, 30, 45, 60 or 80 micromol/kg of BUS. Doses of 15 or 30 micromol/kg of BUS were able to increase DNA-damaged cell frequency, but doses of 45 micromol/kg body weight or higher caused a sudden drop in this frequency. This suggests that higher doses cause lesions that inhibit the expression of damage as comets, i.e., DNA-protein or interstrand crosslinks. The latter could be explained by sudden monoadduct-to-crosslink transformation due to a DNA conformational change induced by monoadduct accumulation that facilitates crosslink formation. This narrow dose-dependent transition could contribute to the narrow therapeutic window of BUS.

Cutaneous, But Not Airway, Latex Exposure Induces Allergic Lung Inflammation and Airway Hyperreactivity in Mice

As respiratory symptoms are common in addition to skin reactions in natural rubber latex allergy, we investigated the significance of different allergen exposure routes in the development of lung inflammation and airway hyperreactivity (AHR). Both intracutaneous (IC) and intraperitoneal (IP) exposure followed by airway challenge with latex proteins induced an influx of mononuclear cells and eosinophils to the lungs. AHR and lung mucus production increased significantly after IC and IP but not after intranasal (IN) exposure. Infiltration of inflammatory cells was associated with the induction of T-helper type 2 (Th2) cytokines and several CC chemokines. Only a marginal induction of these mediators was found after IN exposure. On the contrary, increased levels of transforming growth factor-beta1 and forkhead box 3 mRNA, markers of regulatory activities, were found in the lungs after IN but not after IC exposure. Finally, IC and IP, but not IN, latex exposure induced a striking increase in specific immunoglobulin E (IgE) levels. Cutaneous latex exposure in the absence of adjuvant followed by airway challenge induces a local Th2-dominated lung inflammation and a systemic IgE response. Cutaneous exposure to proteins eluting from latex products may therefore profoundly contribute to the development of asthma in latex allergy.

In vivo Distribution of Bismuth in the Mouse Brain: Influence of Long‐Term Survival and Intracranial Placement on the Uptake and Transport of Bismuth in Neuronal Tissue

Bismuth is used for a multitude of industrial purposes and has partly replaced toxic heavy metals such as lead and mercury in e.g. lubricants and shotgun pellets. In medicine, bismuth-compounds have long been used to remedy gastrointestinal disorders; lately in combination with antibiotics to treat Helicobacter pylori associated peptic ulcers. An epidemic episode of bismuth-induced encephalopathy in France in the 1970s revealed the neurotoxic potential of bismuth. This incidence, involving almost 1000 patients, remains unexplained and the contribution of other factors besides bismuth has been postulated. Recently an autometallographic technique made it possible to detect bismuth in morphologically intact tissue. In the present study, autometallographicly detectable bismuth was seen throughout the brain following intraperitoneal and intracranial exposure. The neuronal staining pattern seems highly organized with some areas heavily stained and others with low or no staining. Long-term (8 months) intraperitoneal exposure led to higher bismuth uptake than short-term (2 weeks) exposure. Following both intraperitoneal and intracranial exposure, high amounts of bismuth were found in the reticular and hypothalamic nuclei, in the oculomotor and hypoglossal nuclei and in Purkinje cells. Within the central nervous system (CNS) retrograde axonal transport was seen after intracranial bismuth exposure. Axonal transport seems to influence the distribution of bismuth as the highest uptake of bismuth after intraperitoneal exposure was seen in the facial and the trigeminal motor nuclei, i.e. neurones with processes outside the blood-brain barrier, whereas these nuclei contained no bismuth following ic exposure. Ultrastructurally, accumulation of bismuth was seen in lysosomes.

Heparin induced thrombocytopaenia secondary to intraperitoneal heparin exposure

Type II immune-mediated heparin-induced thrombocytopenia (HIT) is reported to occur in 2% of individuals exposed to heparin for more than 4 days [1]. HIT has been well described in haemodialysis patients with a similar incidence to non-dialysis patients [2]. Patients treated with peritoneal dialysis are not routinely exposed to heparin during dialysis, and for this reason a switch from haemodialysis to peritoneal dialysis is often considered if HIT occurs in a hemodialysis patient. Previous studies have demonstrated that intraperitoneal heparin does not produce systemic anticoagulation and it has been suggested that a combination of large molecular weight and negative charge prevent systemic absorption of heparin across the peritoneal membrane [3]. However, it is unclear as to whether the reported lack of systemic absorption across the peritoneal membrane protects against the development of HIT. This is an important consideration because in many units it is standard practice to administer intraperitoneal heparin to prevent fibrin clot formation during episodes of peritonitis. In this case report we describe for the first time, to our knowledge, a case of type II HIT in a peritoneal dialysis patient who received intraperitoneal heparin.

Immunotoxicity of Gallium Arsenide on Antigen Presentation: Comparative Study of Intratracheal and Intraperitoneal Exposure Routes

Gallium arsenide (GaAs) is a semiconductor utilized in electronics and computer industries. GaAs exposure of animals causes local inflammation and systemic immune suppression. Mice were administered 2 to 200 mg/kg GaAs. On day 5, intratracheal instillation increased lung weights in a dose-dependent manner and induced pulmonary inflammation exemplified by mononuclear cell infiltration and mild epithelial hyperplasia. No fibrosis, pneumocyte hyperplasia, proteinosis, or bronchial epithelial damage was observed in the lungs. Splenic cellularity and composition were unaffected. GaAs' effect on antigen presentation by macrophages was similar after intratracheal and intraperitoneal exposure, although the lowest observable adverse effect levels differed. Macrophages from the exposure site displayed an enhanced ability to activate an antigen-specific CD4+ helper T-cell hybridoma compared with vehicle controls, whereas splenic macrophages were defective in this function. The chemical's impact on peritoneal macrophages depended on the exposure route. GaAs exposure augmented thiol cathepsins B and L activities in macrophages from the exposure site, but decreased proteolytic activities in splenic macrophages. Alveolar macrophages had increased expression of major histocompatibility complex (MHC) Class II molecules, whereas MHC Class II expression on splenic and peritoneal macrophages was unaffected. Modified thiol cathepsin activities statistically correlated with altered efficiency of antigen presentation, whereas MHC Class II expression did not. Our study is the first one to examine the functional capability of alveolar macrophages after intratracheal GaAs instillation. Therefore, thiol cathepsins may be potential target molecules by which GaAs exposure modulates antigen presentation.

Development of an Oral Exposure Mouse Model to Predict Drug-Induced Hypersensitivity Reactions by Using Reporter Antigens

The capability of certain drugs to cause immune-mediated drug hypersensitivity reactions in susceptible individuals has initiated a search for pre-clinical screening tools to identify immunosensitizing drugs. Since most drugs are taken orally, hazard assessment of their immunosensitizing potential should include oral exposure models. In this study, the predictive value of the reporter antigen (RA) approach was investigated in combination with oral or intraperitoneal (ip) exposure to a selection of allergenic drugs, i.e., D-penicillamine (D-Pen), Diclofenac (DF), or Nevirapine (Nevi). The RA trinitrophenyl-Ovalbumin (TNP-OVA) was used to assess the capacity of the drugs to stimulate systemic immune responses to a bystander antigen, whereas the RA TNP-Ficoll was used to indicate whether the drugs were able to induce specific anamnestic T-cell responses. TNP-OVA was injected (ip) in C3H/HeOuJ mice that were subsequently exposed (orally or ip) to one of the drugs via different exposure protocols. All three model drugs used resulted in delayed type hypersensitivity reactions to TNP-OVA after ip and oral exposure. In addition, TNP-specific serum antibody levels were increased after ip exposure to Nevi, and after both oral and ip exposure to D-Pen and DF. These data indicate that the present drugs are able to stimulate immune responses to bystander antigens. Responses to TNP-Ficoll were measured in the popliteal lymph node of BALB/c mice three weeks after they received a single oral dose of D-Pen or DF. Results of this approach show that orally pre-treated mice responded with enhanced responses (TNP-specific IgG1 and IFN-gamma production) to sub-optimal doses of D-Pen or DF in a drug-specific manner. Data with TNP-Ficoll indicate that these drugs stimulate systemic formation of specific T cells. Together, the RA-approach allows assessment of systemic sensitization upon oral and/or ip exposure to the selected drugs. To further evaluate the utility of these models, more drugs, including non-allergenic drugs and those that require metabolic conversion to become allergenic need to be studied in the present models.

Heritable translocations induced by dermal exposure of male mice to acrylamide

Acrylamide (AA) is an important industrial chemical used mainly in the production of polymers. It can be absorbed through the skin. AA was shown to be a germ cell clastogen that entails a genetic risk for exposed workers. The genetic risk calculation was based on mouse heritable translocation test data obtained after acute intraperitoneal (ip) exposure (Adler et al., 1994). To obtain a correction factor between ip and dermal exposure, dominant lethal and heritable translocation tests were carried out with dermal exposure of male mice to AA. In the dominant lethal test, male (102/El × C3H/El)F₁ mice were exposed by dermal application to the shaved backs of 50 mg/kg AA per day on five consecutive days or to five daily ip injections of 50 mg/kg AA. One day after the end of exposure, the males were mated to untreated females of the same hybrid stock for four days and females were changed every four days for a total of five matings. Dominant lethal effects were found during matings 1–3. For ip exposure, these values were 81.7, 85.7 and 45.4%, respectively; for dermal exposure the corresponding values were 22.1, 30.6 and 16.5%, respectively. In the heritable translocation assay, male C3H/El mice were treated with five dermal exposures of 50 mg/kg AA and mated 1.5–8.5 days after the end of exposure to untreated female 102/El mice. Pregnant females were allowed to come to term and all offspring were raised to maturity. Translocation carriers among the F₁ progeny were selected by a sequential fertility testing and cytogenetic analysis including G-band karyotyping and M-FISH. A total of 475 offspring were screened and 41 translocation carriers were identified. The observed translocation frequency after dermal exposure was 8.6% as compared to 21.9% after similar ip exposure (Adler, 1990). The calculated ratio of ip vs. dermal exposure of 0.39 can be applied to obtain a more realistic calculation of genetic risk for dermally exposed workers.

Physiologically Based Pharmacokinetic/Pharmacodynamic Model for the Organophosphorus Pesticide Diazinon

Diazinon (DZN) is an organophosphorus pesticide with the possibility for widespread exposures. The toxicological effects of DZN are primarily mediated through the effects of its toxic metabolite, DZN-oxon on acetylcholinesterases, which results in accumulation of acetylcholine at neuronal junctions. A physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model was developed to quantitatively assess the kinetics of DZN and its metabolites in blood and the inhibition of cholinesterases in plasma, RBC, brain, and diaphragm. Focused in vivo pharmacokinetic studies were conducted in male Sprague–Dawley rats and the data were used to refine the model. No overt toxicity was noted following doses up to 100 mg/kg. However, cholinesterases in plasma, RBC, brain and diaphragm were substantially inhibited at doses of 50 mg/kg. In plasma, total cholinesterase was inhibited to less than 20% of control by 6 h post dosing with 100 mg/kg. Inhibition of brain acetylcholinesterase (AChE) following 100 mg/kg exposures was approximately 30% of control by 6 h. Diaphragm butyrylcholinesterase (BuChE) inhibition following 100 mg/kg dosing was to less than 20% of control by 6 h. The PBPK/PD model was used to describe the concentrations of DZN and its major, inactive metabolite, 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMHP) in plasma and urinary elimination of IMHP. The fit of the model to plasma, RBC, brain, and diaphragm total cholinesterase and BuChE activity was also assessed and the model was further validated by fitting data from the open literature for intraperitoneal, intravenous, and oral exposures to DZN. The model was shown to quantitatively estimate target tissue dosimetry and cholinesterase inhibition following several routes of exposures. This model further confirms the usefulness of the model structure previously validated for chlorpyrifos and shows the potential utility of the model framework for other related organophosphate pesticides.

Impairment of male reproduction in adult rats exposed to hydroxyprogesterone caproate in utero

Hydroxyprogesterone caproate is one of the most effective and widely used drugs for the treatment of uterine bleeding and threatened miscarriage in women. Hydroxyprogesterone caproate was administered to pregnant rats in order to assess the effect of intraperitoneal exposure to supranormal levels of hydroxyprogesterone caproate on the male reproductive potential in the first generation. The cauda epididymal sperm count and motility decreased significantly in rats exposed to hydroxyprogesterone caproate during embryonic development, when compared with control rats. The levels of serum testosterone decreased with an increase in follicle stimulating hormone and luteinizing hormone in adult rats exposed to hydroxyprogesterone caproate during the embryonic stage. It was suggested that the impairment of male reproductive performance could be mediated through the inhibition of testosterone production.

Impact of leukocytes and platelets in mediating hepatocyte apoptosis in a rat model of systemic endotoxemia.

Apoptotic hepatocytes have been demonstrated to represent an important signal for transmigration of leukocytes sequestered in sinusoids during endotoxemia in vivo. Beside leukocytes, platelets and their adhesion to endothelial cells and leukocytes have been implicated in inflammatory liver injury. Using in vivo multifluorescence microscopy, we examined the possibility that hepatocellular apoptosis causes both leukocytes and platelets to colocalize within the sinusoidal microvasculature of endotoxemic livers. We further addressed the issue whether cellular colocalization with apoptotic hepatocytes is cause or consequence of apoptosis. Intraperitoneal exposure of rats with LPS (5 mg/kg) induced liver injury after 6 and 16 h, as given by nutritive perfusion failure (20 +/- 2 and 21 +/- 2%), intrahepatic leukocyte (60 +/- 10 and 121 +/- 48 cells/mm(2)), and platelet (12 +/- 4 and 34 +/- 4 cells/mm(2)) accumulation as well as parenchymal cell apoptosis (4 +/- 1 and 11 +/- 2 cells/mm(2)) and caspase cleavage (4.7 +/- 2.4- and 7.0 +/- 3.0-fold increase; P < 0.05 vs. saline-exposed controls). Higher doses of LPS (10 mg/kg ip) further increased intrahepatic leukocyte and platelet accumulation but not the extent of parenchymal apoptosis. Detailed spatial analysis revealed colocalization of leukocytes (range 12-24%) but barely of platelets (<6%) with apoptotic hepatocytes in all endotoxemic groups studied. It is of interest, however, that platelets were found at increasing rates in colocalization with leukocytes at 6 and 16 h after LPS exposure (5 mg/kg LPS: 7 +/- 3 and 25 +/- 6%; 10 mg/kg LPS: 11 +/- 4 and 14 +/- 1%). Platelet-leukocyte events significantly correlated with the extent of caspase cleavage as an indicator of tissue apoptosis (P < 0.05; r = 0.82). Blockade of apoptosis by a pan-caspase inhibitor caused a significant reduction of leukocyte adherence and platelet-leukocyte colocalization on LPS exposure. On the other hand, leukocytopenic animals revealed reduced hepatocyte apoptosis, although values still exceeded those of controls, and in leuko- and thrombocytopenic animals, hepatocyte apoptosis was found reduced to control values. Taken together, LPS-associated hepatocyte apoptosis seems to be initiated by circulating blood cells that become adherent within the liver but might also contribute to further sustain the inflammatory cell-cell response.

Aristolochic acid nephropathy and the peritoneum: Functional, structural, and molecular studies

Aristolochic acid nephropathy (AAN) is a rapidly progressive interstitial nephropathy linked to the exposure to aristolochic acid (AA) and characterized by extensive fibrosis and urothelial atypia. Although the fibrotic process has been documented in extrarenal tissues, the involvement of the peritoneum, as well as the efficacy of peritoneal dialysis in AAN patients, remain uncertain. The structure of the peritoneal membrane and the expression of basic fibroblast growth factor (bFGF), collagen type III, endothelial nitric oxide synthase (eNOS), and aquaporin-1 (AQP1) were investigated in peritoneal biopsies from an index AAN patient, four other AAN patients, four regular peritoneal dialysis patients, and two controls. Similar methods were used to investigate a rabbit model of AAN after intraperitoneal exposure to high-dose AA. AA-DNA adducts were screened by 32P-postlabeling analysis. The AAN patients had renal failure, renal fibrosis, and urothelial atypia. The peritoneum of AAN patients had a normal structure, lacked cellular atypia, and, in comparison with regular peritoneal dialysis patients and controls, did not show abnormal regulation of fibrotic and endothelial markers. Furthermore, specific AA-DNA adducts were not identified in the peritoneum of AAN patients. In contrast, AA-DNA adducts were detected in peritoneal and kidney tissues of all exposed rabbits, and one of them developed a malignant mesothelioma. These data demonstrate the lack of fibrotic and vascular alterations and the absence of cellular atypia in the peritoneum from AAN patients. Thus, peritoneal dialysis should not be discouraged in these patients. Nevertheless, studies in a rabbit model of high-dose AA exposure may suggest a potential risk of peritoneal malignancy.

Specific characteristics of peritoneal leucocyte populations during sterile peritonitis associated with icodextrin CAPD fluids.

Icodextrin dialysate used for peritoneal dialysis contains an iso-molar glucose polymer solution, which provides sustained ultrafiltration over long dwell times and is considered a valuable approach to reduce intraperitoneal glucose exposure. However, several side effects have been described, including abdominal pain and allergic and hypersensitivity reactions. Also, reactions compatible with chemical peritonitis have been reported. Over the period of a few months (January 2002-May 2002), a remarkable increase in the number of continuous ambulatory peritoneal dialysis (CAPD) patients using icodextrin dialysate diagnosed with sterile peritonitis was observed in our unit. Five of the CAPD patients using icodextrin dialysate in our unit and diagnosed with sterile peritonitis were screened for leucocyte count and leucocyte differentiation during a follow-up period of 77 +/- 23 days. In addition, expression of CD14, a receptor for lipopolysaccharide (LPS), on the peripheral and peritoneal monocyte population was analysed. These results were compared to CAPD patients suffering from bacterial peritonitis. The peritoneal leucocyte count of CAPD patients using icodextrin dialysate and diagnosed with sterile peritonitis did not decrease significantly before treatment with icodextrin dialysate was interrupted, whereas it currently disappeared within 2-4 days in proven bacterial peritonitis. The sterile, cloudy icodextrin effluent contained an excess of macrophages on the day of diagnosis, whereas in bacterial peritonitis essentially an increase in the granulocyte population was observed. No elevation in the eosinophil population was observed. In contrast to bacterial peritonitis, we observed no increase in CD14 expression on the peripheral and peritoneal macrophages on the day of presentation and during the follow-up period. Specific batches of the icodextrin CAPD fluids contain a macrophage chemotactic agent, which causes a sustained inflammatory state in the peritoneal cavity. Because no increase in the expression of the LPS receptor CD14 could be observed, the increased peritoneal leucocyte count is probably not caused by LPS or LPS-like (possibly peptidoglycan-like) contamination.

Assessment of the inherent allergenic potential of proteins in mice.

There is considerable interest in the design of approaches that will permit the accurate identification and characterization of proteins that have the inherent potential to induce sensitization and cause food allergy. Among the methods used currently as part of such assessments are consideration of structural similarity to, or amino acid sequence homology with, known human allergens; whether there exists immunologic cross-reactivity with known allergens; and measurement of resistance to proteolytic digestion in a simulated gastric fluid. Although such approaches provide information that will contribute to a safety assessment, they do not--either individually or collectively--provide a direct evaluation of the ability of a novel protein to cause allergic sensitization. For this reason, work is in progress to design and evaluate suitable animal models that will provide a more holistic assessment of allergenic potential. In this laboratory, the approach we have taken has been to examine the characteristics of immune responses induced in mice following parenteral (intraperitoneal) exposure to test proteins. The basis of this method is to determine simultaneously the overall immunogenic potential of proteins [measured as a function of immunoglobulin (Ig) G antibody responses] and to compare this with their ability to provoke IgE antibody production, IgE being the antibody that effects allergic sensitization. Although this approach has not yet been evaluated fully, the results available to date suggest that it will be possible to distinguish proteins that have the inherent potential to induce allergic sensitization from those that do not. In this article we summarize progress to date in the context of the scientific background against which such methods are being developed.

Effects of sodium arsenite exposure on development and behavior in the rat

Arsenic is an environmental contaminant found in soil, water and air in some zones of the world. It has been widely studied for its effects as a human carcinogenic agent, but few studies have dealt with neurobehavioral effects. In addition, studies of arsenic effects on development have only addressed its effects on embryotoxicity and teratogenicity after a single oral, gavage or intraperitoneal exposure. Among the behavioral alterations reported after intoxication with arsenic are both increased and decreased locomotor activity and learning deficits in a delayed alternation task [Toxicol. Lett. 54 (1990) 345; Bull. Environ. Contam. Toxicol. 50 (1993) 100; Brain Res. Bull. 55 (2001) 301]. To further characterize developmental and behavioral alterations induced by arsenic exposure, Sprague–Dawley rats were exposed to arsenite (36.70 mg arsenic/l in drinking water) from gestation day 15 (GD 15) or postnatal day 1 (PND 1), until approximately 4 months old. The pregnant or lactating dams received either the arsenic solution or regular drinking water and once pups were weaned, they continued receiving the same solution as drinking water. Animals exposed from GD 15 showed increased spontaneous locomotor activity and both exposed groups showed increased number of errors in a delayed alternation task in comparison to the control group. Total arsenic (TA) content in brain was similar for both exposed groups and significantly different from the control group. These results indicate that rats exposed to arsenic during development present deficits in spontaneous locomotor activity and alterations in a spatial learning task.